People across the UK will wake up having gained an hour’s sleep on Sunday morning, as the clocks go back heralding darker evenings and shorter days. But how much do we know about sleep and its impact on our lives, from our health and mood, to how long we’ll live?
1. We’re told to get our eight hours
We often hear that we should all be getting eight hours’ sleep a night. Organisations from the NHS to the US National Sleep Foundation recommend it. But where does this advice come from?
Studies carried out around the world, looking at how often diseases occur in different groups of people across a population, have come to the same conclusion: both short sleepers and long sleepers are more likely to have a range of diseases, and to live shorter lives. But it’s hard to tell whether it is short sleep that is causing disease or whether it is a symptom of a less healthy lifestyle. Short sleepers are generally defined as those who regularly get less than six hours’ sleep and long sleepers generally more than nine or 10 hours’ a night.
Shane O’Mara, professor of experimental brain research at Trinity College Dublin, says that, while it’s difficult to tell whether poor sleep is a cause or a symptom of poor health, these relationships feed off each other. For example, people who are less fit exercise less, which leads people to sleep badly, become exhausted and less likely to exercise, and so on.
We do know that chronic sleep deprivation – that is, under-sleeping by an hour or two a night over a period of time – has been linked time and again by scientists to poor health outcomes: you don’t have to go for days without sleep to suffer these negative effects.
2. What happens in your body when you don’t sleep enough?
Poor sleep has been linked to a whole range of disorders. A review of 153 studies with a total of more than five million participants found short sleep was significantly associated with diabetes, high blood pressure, cardiovascular disease, coronary heart disease and obesity.
Studies have shown that depriving people of enough sleep for only a few nights in a row can be enough to put healthy adults into a pre-diabetic state. These moderate levels of sleep deprivation damaged their bodies’ ability to control blood glucose levels. One study found participants who had fewer than seven hours of sleep were almost three times more likely to develop a cold than those who slept for seven hours or more.
People who don’t sleep enough also appear to produce too much of the hormone ghrelin, associated with feeling hungry, and not enough of the hormone leptin, associated with feeling full, which may contribute to their risk of obesity.
3. Shift workers who have disturbed sleep get sick more often
Shift work has been associated with a host of health problems. Researchers have found shift workers who get too little sleep at the wrong time of day may be increasing their risk of diabetes and obesity. Shift workers are significantly more likely to report “fair or bad” general health according to a 2013 NHS study, which also found people in this group were a lot more likely to have a “limiting longstanding illness” than those who don’t work shifts.
People who work shifts are significantly more likely to take time off sick, according to figures from the Office for National Statistics. There is a far bigger gap for non-manual workers than manual workers – lack of sleep seems to have a bigger impact on those doing more sedentary jobs.
4. Phones are keeping teenagers awake
Sleep experts say teenagers need up to 10 hours sleep a night, but almost half don’t get this much according to the NHS.
Bedrooms are supposed to be a place of rest but are increasingly filled with distractions like laptops and mobile phones, making it harder for young people to nod off.
We have more different types of entertainment on offer than ever, making the temptation to stay awake greater. The blue light emitted by electronic devices makes us feel less sleepy. And the activity itself – be it talking to friends or watching TV – stimulates our brain when it should be winding down.
Digital Awareness UK and the Headmasters and Headmistresses Conference recommend a nightly “digital detox”, putting mobile devices away for 90 minutes before lights out.
5. Morning larks, night owls?
There have always been morning people and evening people. We even have genetic evidence that backs this up.
But the introduction of artificial light appears to have exacerbated this effect, particularly for people who prefer to stay up late.
If you are already inclined towards being a night owl, artificial light will make you stay up even later.
About 30% of us tend towards being morning people and 30% towards being evening people, with the other 40% of us somewhere in the middle – although marginally more people prefer early rising to late nights.
We do have some control over our body clocks, however. Those who are naturally late to bed and late to rise can try reducing their exposure to light in the evenings and making sure they get more light exposure in the daytime.
A team of researchers took a group of volunteers camping in Colorado, where they had no access to artificial light. Only 48 hours was enough to shift the campers’ body clocks forward by almost two hours.
Levels of melatonin, the hormone that tells our body to prepare for sleep, began rising earlier in the volunteers – their bodies were preparing for sleep much closer to sunset.
Article taken in part from www.bbc.co.uk
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